cuted under the influence of antecedent impressions, and
are therefore controlled by ideas, there seems to have been such an
improvement. Still, however, it is altogether of a physical kind. Every
impression of which the dog or elephant is conscious implies change in
the nerve centres, and these changes are at the basis of the memory
displayed by those animals. Our own experience furnishes many
illustrations. When we gaze steadfastly on some brightly-illuminated
object, and then close or turn aside our eyes, a fading impression of
the object at which we have been looking still remains; or, when a spark
is made to revolve rapidly, we think we see a circle of fire, the
impression upon the retina lasting until the spark has completed its
revolution. In like manner, though far more perfectly, are impressions
registered or stored up in the sensory ganglia, the phantoms of
realities that have once been seen. In those organs countless images may
thus be superposed.

[Sidenote: Analogies between animals and man.] Man agrees with animals
thus approaching him in anatomical construction in many important
respects. He, too, represents a continuous succession of matter, a
continuous expenditure of power. Impressions of external things are
concealed in his sensory ganglia, to be presented for inspection in
subsequent times, and to constitute motives of action. But he differs
from them in this, that what was preparatory and rudimentary in them is
complete and perfect in him. From the instrument of instinct there has
been developed an instrument of intellection. In the most perfect
quadrupeds, an external stimulus is required to start a train of
thought, which then moves on in a determinate way, their actions
indicating that, under the circumstances, they reason according to the
same rules as man, drawing conclusions more or less correct from the
facts offered to their notice. But, the instrument of intellection
completed, it is quickly brought into use, and now results of the
highest order appear. The succession of ideas is under control; new
trains can be originated not only by external causes, but also by an
interior, a spontaneous influence. The passive has become active.
Animals remember, man alone recollects. Every thing demonstrates that
the development and completion of this instrument of intellection has
been followed by the super-addition of an agent or principle that can
use it.

[Sidenote: Points of distinction between th